Field
This disclosure relates generally to electronic circuits, and more specifically, to a low drop-out voltage regulator and method therefor.
Related Art
A low drop out (LDO) voltage regulator is used to provide a stable power supply voltage that does not fluctuate much in response to a changing load. The drop out voltage is the difference in voltage between the power supply and the lowest regulated output voltage. Low drop out voltage regulators are commonly used in battery powered applications.
Many systems-on-a-chip (SoC) integrated circuit applications include analog and radio frequency (RF) circuits and digital circuits on the same integrated circuit. The transistor switching of the digital circuits can cause the power supply to be very noisy while the analog and RF circuits may be sensitive to the power supply noise. Therefore, the analog and RF circuits should be provided with a very clean power supply voltage to avoid performance degradations.
A LDO regulator may include an error amplifier, power output driver, feedback resistive network, and output capacitor. A Miller compensation capacitor has been used to in LDO regulators to provide stability. However, some Miller compensation techniques may require a capacitor to be integrated on-chip. On-chip capacitors of sufficient capacitance may require a substantial surface area of the integrated circuit, thus increasing cost of the integrated circuit. Also, the use of Miller compensation capacitors may cause the LDO regulator to react slowly to changes in the load and increase output voltage glitches and settling time.
One of the main sources of noise in the LDO regulator is caused by power supply noise coupling through the error amplifier, band-gap reference, and the power output driver. If the error amplifier does not have good power supply noise rejection, the error amplifier can degrade the performance the entire regulator. Also, the error amplifier should provide high gain while providing good power supply noise rejection.
Therefore, a need exists for a LDO voltage regulator that solves the above problems.